1. Field of the Invention
The present invention relates generally to the field of optical scanners, and more particularly to an adapter for viewing and scanning transparent media.
2. Related Art
A document scanner converts a visible image such as a photograph, transparency, or printed paper into an electronic form suitable for copying, storing, or processing by a computer. Reflective document scanners typically have a controlled source of light which is reflected off of the surface of a document onto an array of photosensitive devices. The photosensitive devices convert received light intensity into an electronic signal. Transparency scanners pass light through a transparent image such as a photographic positive slide image, or perhaps a photographic negative, and then onto an array of photosensitive devices.
A transparent image may be scanned in a reflective scanner by placing a white surface behind the transparency, slide, negative or other transparent media. In such an arrangement light passes through the transparent media to a white background, reflects off the white background and passes through the transparent media a second time before impinging onto the photosensitive devices. As a result, light is filtered twice by the transparent image. In general, this double filtering creates an unacceptable distortion of gray scale, color, contrast, and other image characteristics of interest.
Reflective document scanners may also be adapted to scan transparent images by providing a separate light source to backlight the image so that the light passes through the transparent media only once. Such scanners, as well as reflective document scanners utilizing a white surface behind the transparent medium, typically employ a separate template, which is generally pre-positioned on the glass reflective image area or platen of the scanner to assist in the arrangement and alignment of the transparent media on the platen prior to scanning. Generally speaking, the process of arranging the transparent media, particularly slides and negatives, within the template on the platen is a time-consuming task. In addition, the scanner light is typically off during this process, thus viewing the slides and/or negatives while positioning them for scanning is impractical if not impossible.
As a general rule, the user may utilize a light source unrelated to the transparency adapter or scanner itself to view the slides and/or negatives prior to scanning to determine which, if any of the slides and/or negatives should be scanned and thereafter stored in memory. The selected slides and/or negatives may then be positioned within the template on the platen. A separate transparency adapter may then be positioned atop of the template and slides to facilitate scanning operations. This practice, however, requires additional equipment, which in turn increases the costs associated with scanning transparent media such as slides and negatives.